Fragrances are generally known, as is the addition of fragrances to products, such as cosmetic products, to improve their odour. The addition of such fragrances can be carried out to mask unpleasant odours in the product, to lend a pleasant odour to the substrate (e.g. the human skin) or merely to improve the overall consumer acceptance of the products in question.
Fragrance oils used within cosmetic compositions usually comprise a multitude of different perfume raw materials (PRMs). Perfume raw materials include many odiferous chemical compounds. A wide variety of chemicals is known for fragrance uses, including, without limitation, certain aldehydes, ketones, alcohols, terpenes, amines, ethers, hydrocarbons, imines, lactones, thiols and esters. Certain naturally occurring plant and animal oils comprising complex mixtures of various chemical components may also be used as fragrances. The individual PRMs which make up a natural oil may be found by reference to journals commonly used by those skilled in the art such as “Perfume and Flavourist” (ISSN: 1041-2905) or “Journal of Essential Oil Research” (ISSN: 0272-2666), which references are incorporated herein by reference in their entirety.
Every PRM differs from other PRMs by several important properties, including individual character and the olfactory detection level, known as the odour detection threshold (ODT). ODT is defined for a given material as the lowest vapour concentration of that material which can be olfactorily detected. The odour detection threshold per se and some odour detection threshold values are discussed in eg “Standardized Human Olfactory Thresholds”, M. Devos et al, IRL Press at Oxford University Press, 1990, and “Compilation of Odor and Taste Threshold Values Data”, F. A. Fazzalar, editor ASTM Data Series DS 48A, American Society for Testing and Materials, 1978. Both of these publications are incorporated by reference.
By bearing in mind properties, such as ODT, PRMs can be blended to develop a fragrance oil with an overall specific character profile. It is usual for the character to be designed to alter and develop over the product use cycle and during the time that the fragrance is deposited on a substrate as the different PRMs evaporate and are detected by the user. For example, PRMs which have a high volatility and low substantivity are commonly used to give an initial impression of characters such as light, fresh, fruity, citrus, green or delicate floral to the fragrance oil—these characters are detected during or soon after application. Such materials are commonly referred to in the field of fragrances as “top notes”. In contrast, the less volatile, and more substantive PRMs are typically used to give characters such as musk, sweet, balsamic, spicy, woody or heavy floral to the fragrance oil which, although detectable soon after application, also last for longer. These materials are commonly referred to as “middle notes” or “base notes”. Skilled perfumers are usually employed to carefully blend PRMs so that the resultant fragrance oils have the desired overall fragrance character profile.
The physical characteristics of the PRMs themselves may limit the overall fragrance character profiles that can be created by perfumers. One limitation is that the characters remaining on a substrate after several hours, particularly from a rinse off product such as a body wash or a shampoo, are typically dominated by musky characters. The prevalence of these residual characters is so great that modern consumers barely notice them any longer and have little interest in them. They perceive these characters as being the odour that the product itself imparts rather than that of the fragrance. It is therefore desirable to deliver fragrances to a substrate whose residual character, particularly after rinsing or washing, is recognizably different from current musky characters.
The PRMs used in the present invention are known, but they are currently used at only low levels and only in combinations of a few PRMs at a time in any given perfume composition. This is because of the low ODTs exhibitted by these PRMs. It has been generally accepted that combining large numbers of PRMs having low ODTs results in the creation of perfumes which are, at the very least, not aesthetically pleasing and unrounded, and which, at most, can be overpowering and quite unpleasant.
WO 02/34225, teaches compositions comprising enduring fragrances, wherein the enduring nature is achieved by means of fragrance encapsulation in materials such as cyclodextrins. These materials are capable of entraping volatile fragrance oils and then releasing them in response to changes in external conditions, such as exposed to moisture. The presence of such encapsulation materials can be disadvantageous, however, in that they may react with other compositional elements and break down. They may also interfere with the lathering ability of rinse-off personal cleansing compositions.